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The effects of atmospheric aerosol, including smoke, on cloudiness are of great interest for understanding the current climate changes. However, the radiative effect of Siberian biomass burning aerosol (SBBA) on clouds in the Arctic has been little studied. Based on simulation with the CHIMERE chemistry transport model and WRF meteorological model, we analyze the processes responsible for origination of the semidirect radiative effect (SDRE) of smoke from Siberian wildfires over snow–ice surfaces in the Arctic, including time- and space-averaged changes in the radiative fluxes, cloud parameters in different cloud levels, and some meteorological characteristics associated with cloud generation due to the radiative effect of (SBBA). The results show that solar radiation scattering by SBBA particles increases the static stability of the atmosphere at altitudes of 2–4 km and suppresses vertical turbulent motions, which decreases the rate of water condensation, the optical thickness of clouds, and the mixing ratio in the medium- and partly lower-level clouds. The decrease in the optical thickness of clouds, in turn, causes origination of positive SDRE of SBBA at the top and bottom of the atmosphere. Radiation absorption by SBBA particles does not play an essential role in these processes, although additionally changes meteorological characteristics. Our results expand fundamental knowledge of aerosol–cloud interactions in the Arctic and can be used for improving climate models. [ABSTRACT FROM AUTHOR]

Mid‐tropospheric Carbonyl sulfide (OCS) retrievals from the Tropospheric Emission Spectrometer (TES) are utilized to study OCS distributions during the dry/wet seasons over the Amazon rainforest. TES OCS retrievals reveal positive OCS anomalies (∼16 ppt) over the central and southern parts of the Amazon during August–October (dry season) compared to January–March (wet season). There is less OCS taken up by vegetation and soil and more OCS released from biomass burning during the dry season, which causes an increase in OCS concentrations. Strong sinking air during the dry season also helps to trap OCS and this contributes to positive OCS anomalies. MOZART‐4 model captures positive OCS anomalies over the central and southern regions of the Amazon and negative OCS anomalies over the northern part of the Amazon, which are similar to those from TES mid‐tropospheric OCS retrievals. Our studies can help us better understand OCS variations and photosynthetic activities. Plain Language Summary: As a photosynthetic tracer, OCS can help us better understand photosynthetic activities, the biosphere‐atmosphere interaction, and the carbon sink. There are positive OCS anomalies (∼16 ppt) over the central and southern parts of the Amazon during August–October (dry season), which is related to reduced OCS uptake from vegetation and soil, enhanced OCS emission from biomass burning, and strengthened sinking air. MOZART‐4 is used to simulate the OCS variations during dry/wet seasons. Model results are similar to those from Tropospheric Emission Spectrometer OCS retrievals. However, there are some differences between the spatial distributions of OCS in the MOZART‐4 model and the satellite retrievals. Results in this study can help us better understand the variability of OCS and photosynthetic activities over the Amazon rainforest, which is the biggest rainforest and one of the largest sinks of OCS. Key Points: Tropospheric Emission Spectrometer OCS concentrations are higher over the central and southern parts of the Amazon during the dry season than the wet seasonHigh OCS concentrations are related to reduced vegetation uptake, enhanced biomass burning, and increased sinking airMOZART‐4 captures the observed positive OCS anomalies over the central and southern Amazon during August–October (dry season) [ABSTRACT FROM AUTHOR]

The kriging-based estimation of the different types of atmospheric particulate matter (PM) pollutions defined in the air quality regulation raises some operational problems because the (co)kriging equations are obtained by minimizing a linear combination of the estimation variances subject to unbiasedness constraints. As a consequence, the estimation process can result in total PM10 concentrations that are less than the PM2.5 concentrations which would be physically impossible. In a previous publication, it was shown that a convenient external drift modeling can reduce the number of spatial locations where the inequality constraint is not satisfied, without completely solving the problem. In this work, the formulation of the cokriging system is modified, inspired by previous works focusing on positive kriging. The introduction of additional constraints on the cokriging weights are presented, leading to a unique and optimal solution to the problem of cokriging under inequality constraints between two variables. Some computational and algorithmic details are introduced. An evaluation of the penalized cokriging is provided by using the European PM monitoring sites dataset: some maps and performance scores are given to assess the relevance of our iterative optimization scheme.

Abstract Mid‐tropospheric Carbonyl sulfide (OCS) retrievals from the Tropospheric Emission Spectrometer (TES) are utilized to study OCS distributions during the dry/wet seasons over the Amazon rainforest. TES OCS retrievals reveal positive OCS anomalies (∼16 ppt) over the central and southern parts of the Amazon during August–October (dry season) compared to January–March (wet season). There is less OCS taken up by vegetation and soil and more OCS released from biomass burning during the dry season, which causes an increase in OCS concentrations. Strong sinking air during the dry season also helps to trap OCS and this contributes to positive OCS anomalies. MOZART‐4 model captures positive OCS anomalies over the central and southern regions of the Amazon and negative OCS anomalies over the northern part of the Amazon, which are similar to those from TES mid‐tropospheric OCS retrievals. Our studies can help us better understand OCS variations and photosynthetic activities.

Interhemispheric transport (IHT) of airmass is an important parameter for understanding the transport of air pollutants in the troposphere. Although the IHT time of surface emissions is about 1.39 years, the mechanisms and location for transport through the tropics and the role of monsoonal circulations are poorly understood due to lacking observational evidence. This study clarifies the transport pathways that connect the Northern and Southern Hemispheres by analyzing global three‐dimensional distributions of methane (CH4), observed by the thermal infrared (TIR) sensor onboard the Greenhouse gases Observation SATellite (GOSAT), and simulations of an atmospheric chemistry‐transport model (ACTM). CH4 has a chemical lifetime of about 1 year in the tropical troposphere and increased quickly to about 100 years in heights of the tropopause and above, which makes CH4 an ideal species for studying IHT. We found that the most active IHT occurs in the altitude region of the upper troposphere, in a layer of 200 hPa below the tropopause. The IHT over tropical South America and Africa is active almost all year long, while in the Asia region there is significant seasonality caused by the South Asian summer monsoon (ASM). We confirm and clarify the influence of zonally asymmetric heating on IHT in the ASM. We highlight an important role of the monsoon‐induced eddy circulation in the cross‐Equator transport of long‐lived trace gases in the extended zone between tropical Africa and Southeast Asia. The zones of the most active IHT are clearly marked and quantified over the Asian, African, and American continents. Plain Language Summary: Materials transport occurs in the Earth's atmosphere by prevailing winds, and the distance traveled by different species depends on their lifetimes and wind speed. Methane is an important greenhouse gas, with a chemical lifetime ranging from about 1 year in the tropical troposphere to more than 100 years at the tropopause and in the stratosphere. Because of the chemical lifetime comparable to the interhemispheric transport (IHT) time scales of about 1.4 years and emissions mostly in the tropical and Northern Hemisphere lands, methane offers a unique opportunity to study the transport pathways between the two hemispheres. The global satellite (GOSAT‐TIR) measurements of methane vertical profiles fulfill the requirements at reasonable measurement accuracy throughout the free troposphere. We also use an atmospheric chemistry‐transport model (ACTM) to test the hypothesis of IHT through tropical Asian, African, and American continents at the upper‐tropospheric altitudes. Key Points: Interhemispheric transport (IHT) ducts are located over the tropical South America, tropical Africa, and Southeast AsiaMost efficient IHT pathways are located at the upper troposphere, in a layer of 200 hPa below the tropopauseThe South Asian summer monsoon has a dual effect on IHT: blocking over the Indian Ocean and enhancement over tropical Africa [ABSTRACT FROM AUTHOR]

Dynamical processes and changes in the ozone layer in the Arctic stratosphere during the winter of 2019–2020 were analyzed using numerical experiments with a chemistry-transport model (CTM) and reanalysis data. The results of numerical calculations using CTM with Dynamic parameters specified from the Modern Era Retrospective analysis for Research and Applications, version 2 (MERRA-2) reanalysis data, carried out according to several scenarios of accounting for the chemical destruction of ozone, demonstrated that both Dynamic and chemical processes contribute significantly to ozone changes over the selected World Ozone and Ultraviolet Radiation Data Centre network stations, both in the Eastern and in the Western hemispheres. Based on numerical experiments with the CTM, the specific Dynamic conditions of winter–spring 2019–2020 described a decrease in ozone up to 100 Dobson Units (DU) in the Eastern Hemisphere and over 150 DU in the Western Hemisphere. In this case, the photochemical destruction of ozone in both the Western and Eastern Hemispheres at a maximum was about 50 DU with peaks in April in the Eastern Hemisphere and in March and April in the Western Hemisphere. Heterogeneous activation of halogen gases on the surface of polar stratospheric clouds, on the one hand, led to a sharp increase in the destruction of ozone in chlorine and bromine catalytic cycles, and, on the other hand, decreased its destruction in nitrogen catalytic cycles. Analysis of wave activity using 3D Plumb fluxes showed that the enhancement of upward wave activity propagation in the middle of March over the Gulf of Alaska was observed during the development stage of the minor sudden stratospheric warming (SSW) event that led to displacement of the stratospheric polar vortex to the north of Canada and decrease of polar stratospheric clouds’ volume.

European Legislation (Directive, 2008/50/EC) requires the Member State to identify the areas where limit or target values are exceeded and to estimate the population exposed to these exceedances. The monitoring network of particulate matter with diameter less than 10 μs (PM 10 ) and 2.5 μm (PM 2.5 ) is homogeneous enough in Western Europe to describe accurately their daily spatial distribution. Daily mapping is required to correctly quantify the population exposed to the exceedances. Geostatistical methods are commonly used in Air Quality to interpolate the observations by taking into account the spatial dependencies between the data. The case of particulate matter is specific: in addition to the total PM 10 observations, there are, for historical reasons, measurements of the so-called non-volatile fraction of the particles. The non-volatile fraction dataset is corrected and used as an observation of the total PM applied for mapping. It provides therefore a meaningful information on the chemical composition of the particles. Along this line, PM 2.5 data, which are a subset of PM 10 , also bring an important information on the spatial distribution of the PM 10 , and conversely. This work demonstrates the importance of keeping an information considered as secondary in the monitoring network and how it is possible to improve the estimation of PM concentrations. An additive modelling for PM 10 and its subset is used to link the explanatory variables between them and the related cokriging is presented. Maps and scores are shown and confronted to univariate kriging estimations throughout the first three months of 2015 in metropolitan France. [ABSTRACT FROM AUTHOR]

The exposure to ambient particulate matter in metropolitan areas is a major health problem. A prerequisite for formulating effective mitigation strategies it to understand the origin of particulate matter in terms of source regions and sectors. We performed a source attribution of particulate matter (PM) for the Berlin agglomeration area covering the period from 2016 to 2018 using the LOTOS-EUROS chemistry transport model. The (3 year-) mean modelled urban background PM 2.5 concentration (10.4 μg/m³) is largely explained by households (3.2 μg/m³) and industry & energy (2.0 μg/m³), while the remaining source sectors contribute the other half. The modelled annual mean urban increment for PM 2.5 is mainly attributed to households (1.6 μg/m³) and traffic (0.5 μg/m³). With respect to its relative shares the PM 10 source attribution looks similar to that of PM 2.5 throughout the year, but with enhanced natural contributions. From a geographical perspective the main source area for the PM 2.5 in Berlin is Germany (5.1 μg/m³) itself, followed by the contributions from transboundary transport (3.4 μg/m³). The German sources could be further split into Berlin (2.6 μg/m³), Brandenburg (0.7 μg/m³) and remaining states of Germany (1.8 μg/m³). About one third of the foreign shares can be attributed to Germany's neighbouring countries Poland and Czech Republic. During episodes these contributions can significantly differ, e.g. in February 2017 the Polish contribution is about 1/3rd. The sectoral contributions agree with previous findings except that our study indicates lower contributions for traffic. The model's underestimation of total PM is largely caused by an underestimation of the coarse mode PM. Both the coarse mode urban increment as well as the regional background concentrations are underestimated by the model, especially during summer. We suggest that the enhanced coarse material (in the city) during warm seasons is predominated by (road) resuspension processes which need more of our attention to further improve our models. • A sectoral and regional source attribution for Berlin was performed. • The most important source sectors for PM are households and industry & energy. • Transboundary contributions are smaller than domestic contributions. • Missing resuspension processes may explain the underestimation of the coarse mode. [ABSTRACT FROM AUTHOR]

The kriging-based estimation of the different types of atmospheric particulate matter (PM) pollutions defined in the air quality regulation raises some operational problems because the (co)kriging equations are obtained by minimizing a linear combination of the estimation variances subject to unbiasedness constraints. As a consequence, the estimation process can result in total PM 10 concentrations that are less than the PM 2.5 concentrations which would be physically impossible. In a previous publication, it was shown that a convenient external drift modeling can reduce the number of spatial locations where the inequality constraint is not satisfied, without completely solving the problem. In this work, the formulation of the cokriging system is modified, inspired by previous works focusing on positive kriging. The introduction of additional constraints on the cokriging weights are presented, leading to a unique and optimal solution to the problem of cokriging under inequality constraints between two variables. Some computational and algorithmic details are introduced. An evaluation of the penalized cokriging is provided by using the European PM monitoring sites dataset: some maps and performance scores are given to assess the relevance of our iterative optimization scheme., Competing Interests: The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (© 2023 The Authors.)

Methane (CH4) plays important roles in atmospheric chemistry and short-term forcing of climate. A clear understanding of atmospheric CHCH4's budget of emissions and losses is required to aid sustainable management of Earth's future environment. We used an atmospheric chemistry-transport model (JAMSTEC's ACTM) for simulating atmospheric CHCH4. A global inverse modeling system has been developed for estimating CHCH4 emissions from 53 land regions for 2002-2012 using measurements at 39 sites. An ensemble of 7 inversions is performed by varying a priori emissions. Global net CHCH4 emissions varied between 505-509 and 524-545 Tg yr-1 during 2002-2006 and 2008-2012, respectively (ranges based on 7 inversion cases), with a step like increase in 2007 in agreement with atmospheric measurements. The inversion system did not account for interannual variations in OH radicals reacting with CHCH4 in the atmosphere. Our results suggest that the recent update of the EDGAR inventory (version 4.2FT2010) overestimated the global total emissions by at least 25 Tg yr-1 in 2010. The increase in CHCH4 emission since 2004 originated in the tropical and southern hemisphere regions, coinciding with an increase in non-dairy cattle stocks by ~10 % from 2002 (with 1056 million heads) to 2012, leading to ~10 Tg yr-1 increase in emissions from enteric fermentation. All 7 ensemble cases robustly estimated the interannual variations in emissions, but poorly constrained the seasonal cycle amplitude or phase consistently for all regions due to the sparse observational network. Forward simulation results using both a priori and a posteriori emissions are compared with independent aircraft measurements for validation. Based on the results of the comparison, we reject the upper limit (545 Tg yr-1) of global total emissions as 14 Tg yr-1 too high during 2008-2012, which allows us to further conclude that the increase in CH4 emissions over the East Asia (mainly China) region was 7-8 Tg yrv-1 between the 2002-006 and 2008-2012 periods, contrary to 1-17 Tg yr-1 in the a priori emissions. [ABSTRACT FROM AUTHOR]

We examine the meteorological responses due to the probable eruption of Mt. Baekdu using an off-line Climate-Chemistry model that is composed of the National Center for Atmospheric Research (NCAR) Climate Atmosphere Model version 3 (CAM3) and a global chemistry transport model (GEOS-Chem). Using the aerosol dataset from the GEOS-Chem driven by GEOS-5 meteorology, experiment and control simulations of the climate model are performed and their meteorological differences between the two simulations are analyzed. The magnitudes of volcanic eruption and column injection height were presumably set to 1/200 of the Mt. Pinatubo eruption and 9 km, respectively. Significant temperature drop in the lower troposphere (850 hPa), which is mainly due to a direct effect of prescribed volcanic aerosols from Mt. Baekdu, has been simulated up to about −4 K. The upper atmosphere (150 hPa) right above the volcano, however, shows significant warming due to the absorption of the infrared radiation by volcanic aerosols. As a result of the volcanic eruption in the climate model, wave-like patterns are shown in both the geopotential height and horizontal wind. The changes in the lower atmospheric temperature are well associated with the modification of the atmospheric circulation through the hydrostatic balance. In spite of limitations in our current simulations due to several underlying assumptions, our results could give a clue to understanding the meteorological impacts from Mt. Baekdu eruptions that are currently attracting considerable public attention. [ABSTRACT FROM AUTHOR]

Abstract: Deterministic models have become essential tools to forecast and map concentration fields of atmospheric pollutants like ozone. Those models are regularly updated and improved by incorporating recent theoretical developments and using more precise input data. Unavoidable differences with in situ measurements still remain, which need to be better understood. This study investigates those discrepancies in a geostatistical framework by comparing the temporal variability of ozone hourly surface concentrations simulated by a chemistry-transport model, CHIMERE, and measured across France. More than 200 rural and urban background monitoring sites are considered. The relationship between modelled and observed data is complex. Ozone concentrations evolve according to various time scales. CHIMERE correctly accounts for those different scales of variability but is usually unable to reproduce the exact magnitude of each temporal component. Such difficulty cannot be entirely attributed to the difference in spatial support between grid cell averages and punctual observations. As a result of this exploratory analysis, the common multivariate geostatistical model, known as the linear model of coregionalization, is used to describe the temporal variability of ozone hourly concentrations and the relationship between simulated and observed values at each observation point. The fitted parameters of the model can then be interpreted. Their distribution in space provides objective criteria to delimitate the areas where the chemistry-transport model is more or less reliable. [Copyright &y& Elsevier]

Abstract: We examine the impacts of aerosols on regional meteorology due to intense Siberian forest fires occurred in May 2003 using both reanalysis data and global model simulations. Our analysis of the NCEP-DOE reanalysis data shows 99% statistical significant changes in meteorological variables over East Asia in May 2003 relative to the 30 years climatology. In particular a significant surface cooling was observed up to −3.5 K over Siberia and extended to the North Pacific region with the surface pressure increases up to 5.6 hPa. Whereas, smoke aerosols affected the large-scale circulations and resulted in the increases in rainfall rates of 2.9 mm day−1 averaged over the NW Pacific (10–35°N, 130–170°E). We use the climate model simulations with and without biomass burning emissions over Siberia to examine the effects of smoke aerosols on the regional meteorology. The simulated results show consistent changes in meteorological variables including surface temperature, surface pressure and precipitation rates with the observations over East Asia and the NW Pacific, which support that the observed changes are likely due to smoke aerosols from the Siberian forest fires. The implication is that smoke aerosols from the forest fires should be properly considered to correctly simulate both regional climate and synoptic scale weather patterns. [Copyright &y& Elsevier]

Dynamical processes and changes in the ozone layer in the Arctic stratosphere during the winter of 2019–2020 were analyzed using numerical experiments with a chemistry-transport model (CTM) and reanalysis data. The results of numerical calculations using CTM with Dynamic parameters specified from the Modern Era Retrospective analysis for Research and Applications, version 2 (MERRA-2) reanalysis data, carried out according to several scenarios of accounting for the chemical destruction of ozone, demonstrated that both Dynamic and chemical processes contribute significantly to ozone changes over the selected World Ozone and Ultraviolet Radiation Data Centre network stations, both in the Eastern and in the Western hemispheres. Based on numerical experiments with the CTM, the specific Dynamic conditions of winter–spring 2019–2020 described a decrease in ozone up to 100 Dobson Units (DU) in the Eastern Hemisphere and over 150 DU in the Western Hemisphere. In this case, the photochemical destruction of ozone in both the Western and Eastern Hemispheres at a maximum was about 50 DU with peaks in April in the Eastern Hemisphere and in March and April in the Western Hemisphere. Heterogeneous activation of halogen gases on the surface of polar stratospheric clouds, on the one hand, led to a sharp increase in the destruction of ozone in chlorine and bromine catalytic cycles, and, on the other hand, decreased its destruction in nitrogen catalytic cycles. Analysis of wave activity using 3D Plumb fluxes showed that the enhancement of upward wave activity propagation in the middle of March over the Gulf of Alaska was observed during the development stage of the minor sudden stratospheric warming (SSW) event that led to displacement of the stratospheric polar vortex to the north of Canada and decrease of polar stratospheric clouds' volume. [ABSTRACT FROM AUTHOR]

The modelling reconstruction of the processes determining the transport and mixing of ozone and its precursors in complex terrain areas is a challenging task, particularly when local-scale circulations, such as sea breeze, take place. Within this frame, the ESCOMPTE European campaign took place in the vicinity of Marseille (south-east of France) in summer 2001. The main objectives of the field campaign were to document several photochemical episodes, as well as to constitute a detailed database for chemistry transport models intercomparison. CAMx model has been applied on the largest intense observation periods (IOP) (June 21–26, 2001) in order to evaluate the impacts of two state-of-the-art meteorological models, RAMS and MM5, on chemical model outputs. The meteorological models have been used as best as possible in analysis mode, thus allowing to identify the spread arising in pollutant concentrations as an indication of the intrinsic uncertainty associated to the meteorological input. Simulations have been deeply investigated and compared with a considerable subset of observations both at ground level and along vertical profiles. The analysis has shown that both models were able to reproduce the main circulation features of the IOP. The strongest discrepancies are confined to the Planetary Boundary Layer, consisting of a clear tendency to underestimate or overestimate wind speed over the whole domain. The photochemical simulations showed that variability in circulation intensity was crucial mainly for the representation of the ozone peaks and of the shape of ozone plumes at the ground that have been affected in the same way over the whole domain and all along the simulated period. As a consequence, such differences can be thought of as a possible indicator for the uncertainty related to the definition of meteorological fields in a complex terrain area. [Copyright &y& Elsevier]

Abstract: This paper aims at presenting a validation of multi-pollutants over Europe with a focus on aerosols. Chemistry-Transport Models are now used for forecast and emission reduction studies not only for gas-phase species but also for aerosols. Comprehensive model-to-data comparisons are therefore required. We present in this paper a preliminary validation study of the Polyphemus system applied over Europe for 2001. The aerosol model is the SIze REsolved Aerosol Model (SIREAM). It is a sectional model that describes the temporal evolution of the size/composition distribution of atmospheric particles containing a mix of black carbon, mineral dust, inorganic species, and primary and secondary organics. In addition to a brief model description, we present an overview of the model validation. A comprehensive set of model-to-data statistics is computed with observational data extracted from three European databases (the EMEP, AirBase and BDQA databases). Model performance criteria are verified for ozone and particulate matter (PM) and its inorganic components. Comparisons of correlations and root mean square errors with those generated by other models run over Europe for 2001 indicate a good performance of the Polyphemus system. Modifications of the system configuration and parameterizations may have a significant impact on error statistics, which may question the robustness of such models. Because large differences exist between databases, the robustness of model-to-data error statistics is also investigated. [Copyright &y& Elsevier]

Abstract: During the summer 2001, several photo-oxidant pollution episodes were documented around Marseilles-Fos-Berre in the South of France within the framework of the ESCOMPTE campaign. The site is composed of large cities (Marseilles, Aix, and Toulon), significant factories (Fos-Berre), a dense road network, and extensive rural area. Both biogenic and anthropogenic emissions are thus significative. Located close to the Mediterranean Sea and framed by the Pyrenees and the Alps Mountains, pollutant concentrations are under the influence of strong emissions as well as a complex meteorology. During the whole summer 2001, the chemistry-transport model CHIMERE was used to forecast pollutant concentrations. The ECMWF forecast meteorological fields were used as forcing, with a raw spatial and temporal resolution of 0.5° and 3 h, respectively. It was observed that even if the synoptic dynamic processes were correctly described, the resolution was not always able to detail small-scale dynamics (sea breezes and orographical winds). To estimate the impact of meteorological forcing on the modeled concentration accuracy, an intercomparison exercise has thus been carried out on the same episode but with two sets of meteorological data: ECMWF data (with horizontal and temporal resolution of 0.5° and 3 h) and data from the mesoscale model RAMS (3 km and 1 h). The two sets of meteorological data are compared and discussed in terms of raw differences as a function of time and location, and in terms of induced discrepancies between the modeled and observed ozone concentration fields. It was shown that even if the RAMS model provides a better description of land–sea breezes and nocturnal boundary layer processes, the simulated ozone time series are satisfactory with the two meteorological forcings. In the context of ozone forecast, the scores are better with ECMWF. This is attributed to the diffusive aspect of these data that will more easily catch localized peaks, while a small error in wind speed or direction in RAMS will misplace the ozone plume. [Copyright &y& Elsevier]

Layers of pollutants are frequently exported from the North American continent over the North Atlantic Ocean. Several intensive experiments were dedicated to study this long-range transport, which frequently occurs over cloud bands. Therefore, the photolytic impact of a persistent cloud layer upon an advected plume of pollutants is an important question and is addressed in the framework of the North Atlantic Regional Experiment (NARE) 1993 experiment, at a distance of 300 km from the continent. The comprehensive RAMS model coupled on-line with a gaseous and an aqueous chemical module is used to follow the chemistry of the photochemically aged plume. A thin cloud layer involves radicals (OH and HO2) and hydrogen peroxide production in the polluted air advected over it and increases the oxidizing capacity of atmosphere. Additional sensitivity tests to study the radiative impact of the accompanying aerosol layer upon the photolysis rates are conducted. It is shown that aerosols moderate this radiative impact due to the cloud layer. [Copyright &y& Elsevier]

Many previous assessments of the global hydrogen budget have used assumed global averages of temperatures and levels of key reactants to calculate the magnitudes of the various sinks. Dry deposition is by far the largest hydrogen sink but has not been considered in detail in previous estimates of the hydrogen budget. Simulations of hydrogen using a global three-dimensional Lagrangian chemistry-transport model and two different dry deposition schemes were compared with surface measurements. An improved dry deposition scheme which included the effects of soil moisture gave better agreement between the modelled hydrogen levels and surface measurements. The seasonal variation in the hydrogen levels was also simulated much more accurately with the new dry deposition scheme. The model results at high southern latitudes were insensitive to the relative partitioning of the sources between fossil fuel combustion and biomass burning. The results indicate a global mean hydrogen dry deposition velocity of 5.3×10-4 m s-1 which is lower than the previously used 7×10-4 m s-1. [ABSTRACT FROM AUTHOR]

Background: Breast cancer is the most frequent cancer in women in industrialized countries. Lifestyle and environmental factors, particularly endocrine-disrupting pollutants, have been suggested to play a role in breast cancer risk. Current epidemiological studies, although not fully consistent, suggest a positive association of breast cancer risk with exposure to several International Agency for Research on Cancer Group 1 air-pollutant carcinogens, such as particulate matter, polychlorinated biphenyls (PCB), dioxins, Benzo[a]pyrene (BaP), and cadmium. However, epidemiological studies remain scarce and inconsistent. It has been proposed that the menopausal status could modify the relationship between pollutants and breast cancer and that the association varies with hormone receptor status., Objective: The XENAIR project will investigate the association of breast cancer risk (overall and by hormone receptor status) with chronic exposure to selected air pollutants, including particulate matter, nitrogen dioxide (NO2), ozone (O3), BaP, dioxins, PCB-153, and cadmium., Methods: Our research is based on a case-control study nested within the French national E3N cohort of 5222 invasive breast cancer cases identified during follow-up from 1990 to 2011, and 5222 matched controls. A questionnaire was sent to all participants to collect their lifetime residential addresses and information on indoor pollution. We will assess these exposures using complementary models of land-use regression, atmospheric dispersion, and regional chemistry-transport (CHIMERE) models, via a Geographic Information System. Associations with breast cancer risk will be modeled using conditional logistic regression models. We will also study the impact of exposure on DNA methylation and interactions with genetic polymorphisms. Appropriate statistical methods, including Bayesian modeling, principal component analysis, and cluster analysis, will be used to assess the impact of multipollutant exposure. The fraction of breast cancer cases attributable to air pollution will be estimated., Results: The XENAIR project will contribute to current knowledge on the health effects of air pollution and identify and understand environmental modifiable risk factors related to breast cancer risk., Conclusions: The results will provide relevant evidence to governments and policy-makers to improve effective public health prevention strategies on air pollution. The XENAIR dataset can be used in future efforts to study the effects of exposure to air pollution associated with other chronic conditions., International Registered Report Identifier (irrid): DERR1-10.2196/15167., (©Amina Amadou, Thomas Coudon, Delphine Praud, Pietro Salizzoni, Karen Leffondre, Emilie Lévêque, Marie-Christine Boutron-Ruault, Aurélie M N Danjou, Xavier Morelli, Charlotte Le Cornet, Lionel Perrier, Florian Couvidat, Bertrand Bessagnet, Julien Caudeville, Elodie Faure, Francesca Romana Mancini, John Gulliver, Gianluca Severi, Béatrice Fervers. Originally published in JMIR Research Protocols (http://www.researchprotocols.org), 15.09.2020.)

This work aims at developing and validating a numerical air quality operational forecasting system that will be applied over Portugal. The CHIMERE model was chosen for the chemistry-transport simulation using the meteorological parameters supplied by the MM5 mesoscale meteorological model, forced by the AVN/NCEP global forecasts. An experiment of 48-hour real-time forecast simulations was performed, on a daily basis, during the four summer months of 2003. The numerical model system is then evaluated against hourly time series of basic meteorological variables and of ozone and NO2 concentrations, collected in several Portuguese monitoring stations included in meteorological and air quality network. Statistical skill scores are discussed and compared with previous studies. The results point this developed model system as a useful tool that can be used and implemented to anticipate pollution episodes, to local and regional air quality management and for population information purpose. [ABSTRACT FROM AUTHOR]